1. Field of the Invention
The present invention generally relates to data displacement system, and more particularly to data displacement bypass system.
2. Description of the Prior Art
In a computer system, many routine control procedure and data related to thereof are always stored up in a EPROM (Erasable Programmable Read Only Memory). For example, BIOS is always stored up in a ROM (Read Only Memory), and the CPU of the computer system could search data according to addresses on the memory.
Please refer to FIG. 1, the computer could comprise a CPU 12 and a ROM 14, wherein the CPU 12 and the ROM 14 are electrically coupled with a plurality of address lines 11, a CS line 13, an OE line 15 and a plurality of data lines 17 respectively. The ROM 14 could receive a plurality of address characters, CS signals and OE signals outputted from the CPU 12 via the plurality of address lines 11, the CS line 13, the OE line 15 respectively, and the output a plurality of data characters via the plurality of data lines 17 according to the plurality of address characters, CS signals and OE signals.
FIG. 2 is a time sequence diagram that the CPU 12 searches in the ROM 14. The ROM 14 outputs the plurality of data characters (D1, D2 . . . and Dn) according to the plurality of address characters (A1, A2 . . . and An) when the CS signal is a low voltage (or a logic value is 0). The plurality of data characters (D1, D2 . . . and Dn) are outputted when the OE signal is the low voltage (or the logic value is 0).
The ROM 14 of the computer system must be fixed, and the data of the ROM must be updated after the ROM 14 is disassembled. Therefore, the ROM 14 must be disassembled and the test ROM must be installed when the computer system needs to be tested. So a system for testing the computer system without disassembling the ROM 14 is necessary.